Biomass Production, Nitrogen Accumulation and Yield in Wheat under Two Tillage Systems and Nitrogen Supply in the Argentine Rolling Pampa

Biomass production and partition, total nitrogen accumulation, grain yield and yield components in wheat were evaluated along two years. In 2000, two tillage systems were analyzed: mouldboard plough and chisel plough, for two cultivars: Buck Poncho and Buck Charrúa, under three fertilization treatments: I) without N, ii) 90 kg N ha 1 in a single dose at sowing and iii) 45 kg N ha 1 at sowing + 45 kg N ha 1 at the end of tillering. In 2001, the tillage systems and fertilization treatments were the same as in the previous year. Buck Yapeyú and Buck Poncho were tested as cultivars. In 2000, during the first stages, biomass production was higher in the Conventional Tillage (CT) treatment than in Chisel (VT). Nevertheless, at maturity, no significant differences were found in biomass or grain production between the tillage systems. There were significant effects of the fertilization treatments on all growth stages analyzed. In 2001, biomass and grain yield were lower than in the previous year. At anthesis, neither the tillage systems nor the fertilization treatments led to significant differences in biomass production. At maturity, the tillage treatments caused significant effects on biomass production, total N accumulation and yield, while the different fertilization treatments no produced any effects. Biomass production, total N accumulation and yield depended on the NO3 availability, which was modified by rainfall amount and distribution and sowing date. Chisel plough was an effective tillage system, when N availability and sowing date were suitable. Nevertheless, when both sowing date and N availability were unfavorable, the conventional tillage produced a better response than that of the non-conventional tillage. When response for fertilization treatments was found, this was independent of the moment and dose applied. Cultivar yields did not show significant differences in each considered year.